This is a Phase I clinical trial to assess the abuse potential of an investigational drug, CGS-20625. This drug may be used as an anxiolytic agent with reduced sedative side effects and a lesser potential for abuse or dependence than benzodiazepine full agonists like alprazolam. The study involves a double-blind crossover design in which the acute effects of CGS-20625 are compared to placebo and alprazolam with subjects having histories of sedative abuse.